The invention relates to an improved wear-resistant composition of materials used for cutting edges of cutting tools. The composition according to the invention can be used on virtually any cutting tool, but, for convenience herein, reference will be made to hand shears.
Conventional techniques for cutting high-strength fibers or fabrics have many problems. Presently, hand shears are made of low carbon steels or tool steels which are heat-treated to form a hard cutting edge. A problem with such tools is that the cutting edges become dull very quickly, and require frequent regrinding, which reduces the hardness and the cutting edge durability is even further reduced.
A hand shear made of zirconia or zirconium oxide has been developed. This shear is very brittle and susceptible to chipping during edge grinding, and is known to shatter into fragments if dropped on a hard substance.
Another known shear consists of a mechanically held, throw-away insert attached to a holder that forms the cutting edge. Misalignment in such a device results in poor cutting.
While the above devices are capable of cutting many low-strength materials, they fail to provide precise blade alignment and blade edge continuity required to cut high-strength fibers such as glass, carbon and aromatic polyamide fibers, and are, therefore, difficult to use and are economically not feasible for such high-strength fibers.
These prior devices employ a relatively low carbon steel that quickly loses hardness during regrinding or, alternatively, they employ a hard, brittle ceramic that is difficult to grind. Also, the cutting edge achieved in these devices is of poor quality relative to the sharpness and durability required to sever the high-strength fibers and fabrics mentioned above.
Conventional hand shears are typically manufactured using old manufacturing techniques which leaves much to be desired when considering both cost and product quality.
Objects of the invention include a tool having a cutting edge of high hardness, low coefficient of friction and extended life edge, a superior cutting edge relative to prior art devices which is economically feasible for commercial production, a hand shear which exhibits superior quality relative to the hardness and coefficient of friction of the cutting edge, a tool of the type described wherein the chemical composition of the ingredients are efficiently combined to provide a superior cutting edge, a tool of the type described wherein the chemical combination of the ingredients can be proportioned to provide a tough cutting edge, or to provide a harder cutting edge or a combination of toughness and hardness, and a device of the type described which permits the manufacture of hand shears employing superior materials for the cutting edge than heretofore practical.